A mobile communication system provides a location service for supplying a location of a terminal to a certain entity periodically or in response to a request, by including a relevant functional part for calculating the location of the terminal in a mobile communication network.
The location service-related network structure varies according to the internal network structure such as 3GPP or 3GPP2. Methods for calculating a current location of a terminal include a cell-ID method for transferring an ID of a cell to which the terminal belongs, a method for measuring the time taken for radio waves of the terminal to reach each base station and calculating the location of the terminal by using trigonometric measurement, and a method using the Global Positioning System (GPS).
In order to provide the location service to a user, considerable signaling and location information should be transferred between the terminal and a location server. The so-called ‘positioning technologies’ that have been standardized for providing such location services, for instance, a location service based upon the location (position) of a mobile terminal, are undergoing rapid widespread dissemination. The positioning technologies can be provided through a user plane and a control plane. A Secure User Plane Location (SUPL) protocol, which is well-known as an example of the positioning technologies, provides the location service through the user plane.
The SUPL protocol is an efficient method for transferring the location information required for the location calculation of a mobile station. The SUPL protocol employs a user plane data bearer so as to transfer positioning assistance information such as GPS assistance, and to carry positioning technology associated protocols between the mobile terminal and a network.
In general, an SUPL network for providing the location service in a location information system includes an SUPL agent, SUPL Location Platform (SLP), and SUPL Enabled Terminal (SET). The SUPL agent refers to a logical service access point using location information which is actually measured. The SLP refers to a SUPL service access point at a network portion where network resources are accessed to obtain the location information. The SET, being a device capable of communicating with the SUPL network using a SUPL interface, supports procedures defined in the SUPL by interworking with the network through the user plane bearer. Here, the SET may be one of a User Equipment (UE) for UMTS, a Mobile Station (MS) for GSM, a laptop computer having a SET function, a Personal Digital Assistant (PDA) or the like. The SET can be various mobile terminals which are connected through a Wideband LAN (WLAN).
In the location information system, a network for which a user has initially registered is called a home network, and when the user moves or roams to another area, other than the home network area, the network of that other area is called a visited network. An SLP in the home network is called an H-SLP (Home-SLP) while an SLP in the visited network is called a V-SLP (Visited-SLP).
When an SUPL procedure starts in the network of such location information system, an SLP to which an external client is first connected is called a Requesting SLP (R-SLP). The R-SLP is a logical entity, which can be the same as the H-SLP or not. An SET aimed to track its current location is defined by a target SET.
The SLP, as a network element, may include an SUPL Positioning Center (SPC) which is an entity for calculating an actual location, and an SUPL Location Center (SLC) for managing other functions of the SLP excluding the function for calculating location information. Here, the SLC handles roaming, resource managing, and the like.
Therefore, the SET can calculate the location information by communicating with the SPC via the SLC (Proxy mode), or calculate the location information by opening a direct connection with the SPC (Non-proxy mode).
A Triggered Location Service in the SUPL provides location information of a target SET when a specific condition (event) occurs. The triggered location service may include a periodic triggered service which periodically provides location information of a target SET, and an area event triggered service which provides location information of a target SET whenever a specific area occurs.
In the current triggered location service, a triggered session would be ongoing once it has been initiated unless an area event has occurred, a service time has expired, or the triggered session is forcibly terminated. Once the triggered session has been initiated, the session would last for a long period of time. In this instance, a target SET may have a difficulty in maintaining the ongoing triggered session due to a certain condition, or desires to temporarily terminate (end) the ongoing triggered session for its privacy. In such cases, from a perspective of a party which has requested the triggered location service, the ongoing triggered session is unilaterally terminated. The service requesting party should request the triggered location service again from the network (the network performing the triggered location service). This may cause an inconvenience to the requesting party (i.e., user) from the perspective of a service user, and a waste of network resources from the perspective of the network.